Rab6 Is Required for Multiple Apical Transport Pathways but Not the Basolateral Transport Pathway in Drosophila Photoreceptors

PLoS Genet. 2016 Feb 18;12(2):e1005828. doi: 10.1371/journal.pgen.1005828. eCollection 2016 Feb.

Abstract

Polarized membrane trafficking is essential for the construction and maintenance of multiple plasma membrane domains of cells. Highly polarized Drosophila photoreceptors are an excellent model for studying polarized transport. A single cross-section of Drosophila retina contains many photoreceptors with 3 clearly differentiated plasma membrane domains: a rhabdomere, stalk, and basolateral membrane. Genome-wide high-throughput ethyl methanesulfonate screening followed by precise immunohistochemical analysis identified a mutant with a rare phenotype characterized by a loss of 2 apical transport pathways with normal basolateral transport. Rapid gene identification using whole-genome resequencing and single nucleotide polymorphism mapping identified a nonsense mutation of Rab6 responsible for the apical-specific transport deficiency. Detailed analysis of the trafficking of a major rhabdomere protein Rh1 using blue light-induced chromophore supply identified Rab6 as essential for Rh1 to exit the Golgi units. Rab6 is mostly distributed from the trans-Golgi network to a Golgi-associated Rab11-positive compartment that likely recycles endosomes or transport vesicles going to recycling endosomes. Furthermore, the Rab6 effector, Rich, is required for Rab6 recruitment in the trans-Golgi network. Moreover, a Rich null mutation phenocopies the Rab6 null mutant, indicating that Rich functions as a guanine nucleotide exchange factor for Rab6. The results collectively indicate that Rab6 and Rich are essential for the trans-Golgi network-recycling endosome transport of cargoes destined for 2 apical domains. However, basolateral cargos are sorted and exported from the trans-Golgi network in a Rab6-independent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Animals, Genetically Modified
  • Drosophila / drug effects
  • Drosophila / genetics
  • Drosophila / metabolism*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Endosomes / metabolism
  • Ethyl Methanesulfonate / pharmacology
  • Golgi Apparatus / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mutagenesis
  • Mutation
  • Photoreceptor Cells, Invertebrate / metabolism*
  • Protein Transport
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • Drosophila Proteins
  • Membrane Proteins
  • Rab6 protein
  • Rip11 protein, Drosophila
  • Ethyl Methanesulfonate
  • Rab11 protein, Drosophila
  • Rab6 protein, Drosophila
  • rab GTP-Binding Proteins

Associated data

  • Dryad/10.5061/dryad.B971K

Grant support

This work was supported by the Naito Foundation (25-040920), the Novartis Foundation (25-050421), the Hayashi Memorial Foundation for Female Natural Scientists (25-051022), and KAKENHI (21687005, 21113510, and 23113712) to ASK (used for screening). PRESTO (25-J-J4215) is used for analysis for Rab6 mutant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.